Pyridyl Mono-Carboxylate Auxiliary Metal-Azido Magnetic Compounds: Synthese, Structure And Property

Coordination polymers are a new kind of molecular materialswhich have infinite metal-ligand backbones connected bycoordination bonds. It has been undergoing swiftly developmentsine first appeared in1960s. Considering the diversity of organicmolecules, coordination polymers have versatile structures andproperties, giving them very good potential in adsorptive, molecularseparation/exchange, catalytic, electronic, magnetic, and opticalapplications, and consequently attract wide attention fromchemists around the world nowadays. Even so, the presumptiveassembly based on designated precursors currently remains achallenge. As for molecular magnetic materials, in attempt toconstructing structurally and magnetically preferable coordinationpolymers, investigators′tactic often use versatile short bridginggroups incorporating coligand to modulate magnetic interaction andstructural dimension. Azide is an excellent candidate for thepropagation of magnetic interaction between paramagnetic metalcenters as encompassing bountiful coordination modes. Thisdissertation is mainly focus on syntheses, structures andproperties of azide bridged metal-organic complexes with pyridylmono-carboxylate as auxiliary ligand, more details as follows: Initially, part one briefly introduces the solvothermal method,basic theory of magnetism and development of molecular-basedmagnetic materials, and then the definition of single-molecularmagnet and single-chain magnet. Azide involved coordinationpolymers’ magnetic behaviors, magneto-structural correlation andtheir recent advances were emphasized subsequently.Two azido-based complexes with1D chain structure,Cu₁₁（pa）₆（N₃）₁₆（1） and Co₅（pa）₆（N₃）₄（2）, have been obtained throughreaction of picolinic acid combined with azide and metal salts underthe condition of solvothermal synthesis. Compound1is arung-missed chain linked by double μ1,1（EO） modes of azide andfurther formed a3D supermolecular structure via the non-classicalhydrogen bond between the adjacent chains. Notably, the shortdistance of interchain Cu atoms in1lie in the range of sum of vander Waals radius of two Cu（II） atoms, which means weak Cu-Cuinteraction could provide with potential superexchange pathway.Therefore, it might be responsible for the abnormality of magneticbehavior. Compound2was formed by the alternating linkage ofbutterfly-like tetranuclear [Co₄（N₃）₂] cluster with double μ_1,1,1-N₃modes and independent Co atom via EO mode. Detailed magneticmeasurem-ents in direct and alternate current field indicated thatcompound2is a ferromagnetic homospin single-chain magnet.Pyridyl mono-carboxylate auxiliary metal-azido system includinghomometallic and heterometallic compounds is displayed in thispart. Their chemical formulae are Co₃（isopa）₄（N₃）₂（3）, Na₂Mn₂（-N₃）₄（pa）₂（4） and NaCo₃Mn₃O（pa）₆（N₃）₃（NO₃）₂（5）, respectively.Compound3is a3D homometallic network composed of linear Co₃ units. And ferromagnetic coupling probably is transmitted by singleEO azide and O bridge between adjacent Co atoms in each unit.Contrary to3, compound4is an antiferromagnetic heterometallicframework including four different coordination modes of azide, EO,μ1,3（EE）, μ1,1,3,3and μ1,1,1,3,3,which rarely gather toward identicalpolymer. Significantly, compound5with an unprecedented2Dwheel-shaped heterometallic sheet shows a spin canted anti-ferromagnetic behavior testified by the analysis of magneticmeasuremnets.Finally, a concise conclusion was drawn and an outlook of thisresearch area was anticipated.